Machines X and Y work at their respective constant rates. How many more hours does it take machine Y...

[BTGmoderatorLU]

Source: GMAT Prep

Machines X and Y work at their respective constant rates. How many more hours does it take machine Y, working alone, to fill a production order of a certain size than it takes machine X, working alone?

1) Machines X and Y, working together, fill a production order of this size in two-thirds the time that machine X, working alone, does.

2) Machine Y, working alone, fills a production order of this size in twice the time that machine X, working alone, does.

The OA is E

[Jay@ManhattanReview]

Source: GMAT Prep

Machines X and Y work at their respective constant rates. How many more hours does it take machine Y, working alone, to fill a production order of a certain size than it takes machine X, working alone?

1) Machines X and Y, working together, fill a production order of this size in two-thirds the time that machine X, working alone, does.

2) Machine Y, working alone, fills a production order of this size in twice the time that machine X, working alone, does.

The OA is E

Let's take each statement one by one.

1) Machines X and Y, working together, fill a production order of this size in two-thirds the time that machine X, working alone, does.

Say Machine X takes 3x hours, thus, machines X and y would take 2x hours. Say Machine Y takes y hours.

Thus, 1/3x + 1/y = 1/62x

y = 6x hours

Thus, Machine Y, working alone, would take 6x – 3x = 3x hours than Machine X, working alone; however, the value of x is not known. We can't get the answer.

2) Machine Y, working alone, fills a production order of this size in twice the time that machine X, working alone, does.

Certainly insufficient.

(1) and (2) together

Since Statement 2 gives the same result as Statement 1 gives, both statements together are insufficient.

The correct answer: E

Hope this helps!

-Jay
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